Near-field antennas for accumulating energy at a near-field distance with minimal far-field gain

ABSTRACT

An example non-inductive, resonant near-field antenna includes: (i) a conductive plate having first and second opposing planar surfaces and one or more cutouts extending through the conductive plate from the first surface to the second surface; (ii) an insulator; and (iii) a feed element, separated from the first surface of the conductive plate by the insulator, configured to direct a plurality of RF power transmission signals towards the conductive plate. At least some of the plurality of RF power transmission signals radiate through the cutout(s) and accumulate within a near-field distance of the conductive plate to create at least two distinct zones of accumulated RF energy at each of the cutout(s). Furthermore, the at least two distinct zones of accumulated RF energy at the cutout(s) are defined based, at least in part, on a set of dimensions defining each of the cutout(s) and an arrangement of the cutout(s).

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/718,060, filed on Dec. 17, 2019, entitled “Fabrication Of Near-FieldAntennas For Accumulating Energy At A Near-Field Distance With MinimalFar-Field Gain,” which is a continuation of U.S. patent application Ser.No. 15/973,991 (now U.S. Pat. No. 10,511,097), filed on May 8, 2018,entitled “Near-Field Antennas For Accumulating Energy At A Near-FieldDistance With Minimal Far-Field Gain,” which claims priority to U.S.Provisional Patent Application No. 62/505,813, filed May 12, 2017,entitled “Near-Field Antennas for Accumulating Radio Frequency Energy ata Near-Field Distance with Minimal Far-Field Gain,” and U.S. ProvisionalPatent Application No. 62/506,556, filed May 15, 2017, entitled“Near-Field Antennas for Accumulating Radio Frequency Energy at aNear-Field Distance with Minimal Far-Field Gain.” each of which isherein fully incorporated by reference in its respective entirety.

TECHNICAL FIELD

The present disclosure relates generally to wireless power transmission,and more particularly to near-field antennas (e.g., non-inductive,resonant near-field antennas) that accumulate energy at a near-fielddistance to wirelessly deliver power to a receiver.

BACKGROUND

Portable electronic devices such as smartphones, tablets, notebooks andother electronic devices have become a necessity for communicating andinteracting with others. The frequent use of portable electronicdevices, however, uses a significant amount of power, which quicklydepletes the batteries attached to these devices. Inductive chargingpads and corresponding inductive coils in portable devices allow usersto wirelessly charge a device by placing the device at a particularposition on an inductive pad to allow for a contact-based charging ofthe device due to magnetic coupling between respective coils in theinductive pad and in the device.

Conventional inductive charging pads, however, suffer from manydrawbacks. For one, users typically must place their devices at aspecific position and in a certain orientation on the charging padbecause gaps (“dead zones” or “cold zones”) exist on the surface of thecharging pad. In other words, for optimal charging, the coil in thecharging pad needs to be aligned with the coil in the device in orderfor the required magnetic coupling to occur. Additionally, placement ofother metallic objects near an inductive charging pad may interfere withoperation of the inductive charging pad, so even if the user placestheir device at the exact right position, if another metal object isalso on the pad, then magnetic coupling still may not occur and thedevice will not be charged by the inductive charging pad. This resultsin a frustrating experience for many users as they may be unable toproperly charge their devices. Also, inductive charging requires arelatively large receiver coil to be placed within a device to becharged, which is less than ideal for devices where internal space is ata premium.

Charging using electromagnetic radiation (e.g., microwave radiationwaves) offers promise, but RF charging is typically focused on far-fieldcharging and not near-field charging where the device to be charged isplaced on top of the RF energy transmitter. Furthermore, controllingfar-field gain is a challenge that also must be solved to avoid causinginterference with other devices operating in certain frequency bands(e.g., microwave frequency bands).

SUMMARY

Accordingly, there is a need for a near-field wireless charging solutionthat (i) accumulates energy at a near-field distance to wirelesslydeliver power to a receiver, (ii) minimizes far-field gain so as toavoid interference with other devices and comply with governmentguidelines and regulations, and (iii) allows users to place theirdevices at any position on a pad and still receive wireless deliveredenergy. In some embodiments, these charging pads include a plurality ofnear-field antennas (e.g., non-inductive resonant near-field antennas),and a method of operating one such near-field antenna is describedbelow.

For the purposes of this disclosure, the near-field antennas describedherein are referred to interchangeable as unit cell antennas, NFantennas, and non-inductive resonant antennas. Also, references tonear-field transmission cover the radiation of electromagnetic waves fordistances up to and including 1 to 5 millimeters away from a surface ofa charging pad transmitter, while references to far-field transmissioncover radiation of electromagnetic waves for distances over 5millimeters (and up to 30 feet away from a far-field transmitter). Insome instances, references to near-field transmission cover theradiation of electromagnetic waves for distances up to a quarterwavelength of an operating frequency (e.g., a quarter wavelength of anoperating frequency of 5.8 GHz is approximately 12.922 millimeters). Insome embodiments, the operating frequency ranges from 400 MHz to 60 GHz.

(A1) In some embodiments, a method of operating a near-field antennaincludes, providing a near-field antenna that includes a conductiveplate having first and second opposing planar surfaces, and one or morecutouts (also referred to herein as one or more slots) extending throughthe conductive plate from the first surface to the second surface. Thenear-field antenna also includes a feed element separated from the firstsurface of the conductive plate by an insulator. The method furtherincludes causing the feed element to direct a plurality of RF powertransmission signals towards the conductive plate and receiving, at theconductive plate, the plurality of RF power transmission signals fromthe feed element. The method further includes radiating, through the oneor more cutouts, at least some of the plurality of RF power transmissionsignals so that RF energy from the plurality of RF power transmissionsignals accumulates within a near-field distance of the conductive plateto create at least two distinct zones of accumulated RF energy at eachof the one or more cutouts. The at least two distinct zones ofaccumulated RF energy at each of the one or more cutouts are definedbased, at least in part, on: (i) a set of dimensions defining each ofthe one or more cutouts, and (ii) an arrangement of the one or morecutouts.

(A2) In some embodiments of the method of A1, a first cutout of the oneor more cutouts forms a first meandering line pattern and a secondcutout of the one or more cutouts forms a second meandering linepattern.

(A3) In some embodiments of the method of A2, a shape of the firstmeandering line pattern mirrors a shape of the second meandering linepattern, the first and second meandering line patterns have the same setof dimensions, and the shape of the first meandering line pattern isrotated (e.g., rotated 180 degrees) with respect to the shape of thesecond meandering line pattern. For example, the shape of the firstmeandering line pattern is interleaved with the shape of the secondmeandering line pattern (e.g., two U-shaped patterns with a leg of eachU-shaped pattern being interleaved or interposed between the two legs ofthe other U-shaped pattern, as shown in FIG. 2 and described in moredetail below). Alternatively, in some embodiments, a single cutout formsa symmetrical meandering line pattern (e.g., as shown in FIG. 5A).

(A4) In some embodiments of the method of any of A1-A3, a respectivecutout of the one or more cutouts has a respective length that is atleast as large as a wavelength of a respective RF power transmissionsignal of the plurality of RF power transmission signals.

(A5) In some embodiments of the method of A4, the respective cutoutincludes, at least: (i) a first cutout portion defined in a firstdirection, and (ii) a second cutout portion defined in a seconddirection, the second direction being orthogonal to the first direction.Furthermore, a first of the at least two distinct zones of accumulatedRF energy is created at the first cutout portion (e.g., formed along thefirst cutout portion and along the first direction) and a second of theat least two distinct zones of accumulated RF energy is created at thesecond cutout portion (e.g., formed along the second cutout portion andalong the second direction).

(A6) In some embodiments of the method of any of A1-A5, the feed elementis a component of a patch antenna, where the insulator is disposedbetween the feed element and the conductive plate.

(A7) In some embodiments of the method of any of A1-A5, the feed elementis a component of a patch antenna that is at least partiallyencapsulated within the insulator.

(A8) In some embodiments of the method of any of A1-A7, the insulator isselected from the group consisting of: a polymer, a fiber reinforcedpolymer, glass, and air.

(A9) In some embodiments of the method of any of A1-A8, the at least twodistinct zones cover at least 80% of a surface area of the secondsurface of the conductive plate.

(A10) In some embodiments of the method of any of A1-A9, the at leasttwo distinct zones cover at least 90% of the surface area of the secondsurface of the conductive plate.

(A11) In some embodiments of the method of any of A1-A10, the at leasttwo distinct zones of accumulated RF energy extend no more than 5millimeters (mm) above the second surface of the conductive plate.

(A12) In some embodiments of the method of any of A1-A11, the at leasttwo distinct zones of accumulated RF energy extend no more than 4millimeters above the second surface of the conductive plate.

(A13) In some embodiments of the method of any of A1-A12, the at leasttwo distinct zones of accumulated RF energy extend no more than 3millimeters above the second surface of the conductive plate.

(A14) In some embodiments of the method of any of A1-A13, the pluralityof RF power transmission signals are transmitted at a frequency selectedfrom the group consisting of: 5.8 GHz, 2.4 GHz, and 900 MHz.

(A15) In some embodiments of the method of any of A1-A14, the near-fieldantenna is a first near-field antenna and is part of a near-fieldcharging pad (e.g., transmitter pad 100, FIGS. 1A-1B) that also includesa second near-field antenna that is positioned adjacent to the firstnear-field antenna within the near-field charging pad. Furthermore,respective cutouts associated with the second near-field antenna arerotated relative to the one or more cutouts associated with the firstnear-field antenna.

(A16) In some embodiments of the method of any of A1-A15, the feedelement receives the one or more RF power transmission signals from apower amplifier in response to determining that a wireless powerreceiver is placed within a predetermined distance of the surface.

(A17) In some embodiments of the method of A16, the predetermineddistance is less than approximately 5 mm away from the surface.

(A18) In some embodiments of the method of A17, the predetermineddistance is monitored by measuring a signal strength level associatedwith a transmission received by a processor connected to (e.g., inelectrical communication with) the near-field antenna and the signalstrength level is associated with a broadcasted signal received from thewireless power receiver.

(A19) In some embodiments of the method of any of A1-A18, the feedelement and the insulator are surrounded by a conductive housing.Furthermore, the conductive housing defines an opening at one end of thehousing and the conductive plate closes the opening.

(A20) In some embodiments of the method of any of A1-A19, the conductiveplate is a first conductive plate, and the near-field antenna furtherincludes another insulator (e.g., a dielectric layer) disposed on thesecond surface of the first conductive plate and a second conductiveplate disposed on top of the other insulator. In some embodiments, thesecond conductive plate includes one or more additional cutouts.Alternatively, in some embodiments, instead of a second conductiveplate, the near-field antenna further includes a conductive layerdeposited on a surface of the other insulator.

(A21) In some embodiments of the method of any of A1-A20, the conductiveplate is a conductive layer deposited on a surface of the insulator.Alternatively, in some embodiments, the insulator is a dielectric layerthat is deposited on the first surface of the conductive plate.

(A22) In some embodiments of the method of any of A1-A21, the insulatoris a first insulator, and the near-field antenna further includes asecond insulator that separates the feed element from a grounding plate(e.g., grounding plate 308, FIG. 3A).

(A23) In one other aspect, a near-field antenna is provided, and thenear-field antenna includes the structural characteristics for anear-field antenna described above in A1-A22, and the near-field antennais also configured to perform the method steps described above inA1-A22.

(A24) In another aspect, a transmitter pad that includes a plurality ofnear-field antennas is provided. In some embodiments, the transmitterpad includes at least one near-field antenna, one or more communicationscomponents, one or more processors, and memory storing one or moreprograms, which when executed by the one or more processors cause thetransmitter pad to perform the method described in any one of A1-A22.

(A25) In yet another aspect, a transmitter pad (that includes aplurality near-field antennas) is provided and the transmitter padincludes means for performing the method described in any one of A1-A22.

(A26) In still another aspect, a non-transitory computer-readablestorage medium is provided. The non-transitory computer-readable storagemedium stores executable instructions that, when executed by atransmitter pad (that includes a plurality of near-field antennas) withone or more processors/cores, cause the transmitter pad to perform themethod described in any one of A1-A22.

(B1) In some embodiments, a method of fabricating a near-field antennaincludes selecting a set of dimensions for one or more cutouts to bedefined through a conductive plate of a near-field antenna, theconductive plate having opposing first and second planar surfaces. Themethod further includes forming the one or more cutouts through thefirst and second surfaces of the conductive plate in a predefinedarrangement, each of the one or more cutouts having the set ofdimensions. The method further includes coupling an insulator to thefirst surface of the conductive plate and coupling a feed element to theinsulator. In some embodiments, the fabricated near-field antennaincludes the structural characteristics for a near-field antennadescribed above in A1-A22, and the near-field antenna is also configuredto perform the method steps described above in A1-A22.

(C1) In yet another aspect, a near-field antenna is provided. Thenear-field antenna includes: (i) a feed element configured to direct aplurality of radio frequency (RF) power transmission signals towards aconductive plate, (ii) a first slot defined through the conductive platehaving a length that is at least as large as a wavelength of arespective RF power transmission signal of the plurality of RF powertransmission signals transmitted by the feed element, and (iii) a secondslot defined through the conductive plate that interlocks with the firstslot and also has a length that is at least as large as the wavelengthof the respective RF power transmission signal. Further, upon conductionof the plurality of RF power transmission signals via the first andsecond slots, at least two distinct zones of accumulated RF energy formalong the length of each of the first and second slots. The near-fieldantenna includes the structural characteristics for a near-field antennadescribed above in A1-A22, and the near-field antenna is also configuredto perform the method steps described above in A1-A22.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

So that the present disclosure can be understood in greater detail, amore particular description may be had by reference to the features ofvarious embodiments, some of which are illustrated in the appendeddrawings. The appended drawings, however, merely illustrate pertinentfeatures of the present disclosure and are therefore not to beconsidered limiting, for the description may admit to other effectivefeatures.

FIGS. 1A-1B show diagrams illustrating a representative transmitter padin accordance with some embodiments.

FIG. 2 is a schematic of a top section of a transmitter pad, inaccordance with some embodiments.

FIGS. 3A-3D show cross-sectional views of a transmitter pad, inaccordance with some embodiments.

FIGS. 4A-4C show various views of a respective near-field antenna of atransmitter pad, in accordance with some embodiments.

FIGS. 5A-5B show top views of a respective near-field antenna of atransmitter pad, in accordance with some embodiments.

FIG. 6 is a flow diagram showing a method of operating a near-fieldantenna, in accordance with some embodiments.

FIG. 7 is a flow diagram showing a method of fabricating a near-fieldantenna, in accordance with some embodiments.

FIG. 8 shows various power distributions (e.g., accumulations of energy)formed on a transmitter pad, in accordance with some embodiments.

FIG. 9 is a graph that shows an example radiation pattern for a unitcell antenna that includes one or more cutouts.

In accordance with common practice, the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may not depict all of the componentsof a given system, method or device. Finally, like reference numeralsmay be used to denote like features throughout the specification andfigures.

DETAILED DESCRIPTION

Numerous details are described herein in order to provide a thoroughunderstanding of the example embodiments illustrated in the accompanyingdrawings. However, some embodiments may be practiced without many of thespecific details, and the scope of the claims is only limited by thosefeatures and aspects specifically recited in the claims. Furthermore,well-known processes, components, and materials have not been describedin exhaustive detail so as not to unnecessarily obscure pertinentaspects of the embodiments described herein.

FIG. 1A is a high-level block diagram of a transmitter pad 100, inaccordance with some embodiments. The transmitter pad 100 (also referredto herein as near-field radio-frequency (RF) charging pad or near-fieldcharging pad) includes components 102. The transmitter pad is configuredto generate controlled, near-field accumulations of electromagneticenergy that are provided to a receiver that is placed near or on top of(e.g., within 5 mm of a surface of the transmitter pad 100). Forexample, FIG. 1B illustrates a wireless power receiver 120 (e.g., areceiver coupled to or housed within any type of electronic device thatrequires electricity to operate) placed on top of the transmitter pad100 that is harvesting energy from the near-field accumulations ofelectromagnetic energy to charge or power a device coupled to thewireless power receiver. In the descriptions herein, radio frequency(RF) power transmission waves are used as a primary illustrativeexample, but one or ordinary skill in the art will appreciate in view ofthese descriptions that any type of electromagnetic radiation waves maybe used instead in certain embodiments or implementations.

The components 102 of the transmitter pad 100 include, for example, oneor more processor(s) 104, a memory 106, one or more unit cell antennas110 (also referred to herein as near-field antennas), one or morecommunications components 112, and/or one or more transmitter sensors114. In some embodiments, these components 102 are interconnected by wayof a communications bus 108. In some embodiments, the components 102 arehoused within the transmitter pad 100. Alternatively, in someembodiments, one or more of the components 102 are disposed outside(e.g., external) the transmitter pad 100. For example, the one or moreprocessor(s) 104, the memory 106, the one or more communicationscomponents 112, may be external while the one or more unit cell antennas110 and the one or more transmitter sensors 114 may be internal (or someother combination/arrangement of components).

In some embodiments, the communication component(s) 112 include, e.g.,hardware capable of data communications using any of a variety ofwireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6LoWPAN, Thread,Z-Wave, Bluetooth Smart, ISA100.11a, WirelessHART, MiWi, etc.) wiredprotocols (e.g., Ethernet, HomePlug, etc.), and/or any other suitablecommunication protocol, including communication protocols not yetdeveloped as of the filing date of this document.

In some embodiments, the communications component 112 transmitscommunication signals to the receiver 120 by way of the electronicdevice. For example, the communications component 112 may conveyinformation to a communications component of the electronic device(e.g., electronic device 210, FIG. 2), which the electronic device mayin turn convey to the receiver 120 (e.g., via a bus).

In some embodiments, the receiver 120 includes a communicationscomponent configured to communicate various types of data with thetransmitter pad 100, through a respective communication signal generatedby the receiver-side communications component. The data may includelocation indicators for the receiver 120, a power status of theelectronic device, status information for the receiver 120, statusinformation for the electronic device, status information about thepower waves, and/or status information for accumulations of energy(e.g., the distinct zones). In other words, the receiver 120 may providedata to the transmitter pad 100, by way of a communication signal,regarding the current operation of the transmitter pad 100 (or a currentoperation of a unit cell), including: information identifying a presentlocation of the receiver 120, an amount of energy (i.e., usable power)received by the receiver 120, and an amount of usable power receivedand/or used by the electronic device, among other possible data pointscontaining other types of information. This information may be used bythe transmitter pad 100 in conjunction with the embodiments describedherein.

In some embodiments, the data contained within communication signals isused by the electronic device, the receiver 120, and/or the transmitterpad 100 for determining adjustments of the one or more characteristicsused by the unit cell antenna 110 to transmit the power waves. Using acommunication signal, the transmitter pad 100 receives data that isused, e.g., to identify receivers 120 on the transmitter pad 100,identify electronic devices, determine safe and effective waveformcharacteristics for power waves, and/or hone the placement of theaccumulations of energy. In some embodiments, the receiver 120 uses acommunication signal to communicate data for, e.g., alerting thetransmitter pad 100 that the receiver 120 has or is about to be placedon the transmitter pad 100, provide information about electronic device,provide user information that corresponds to electronic device, indicatethe effectiveness of received power waves, and/or provide updatedcharacteristics or transmission parameters that are used to form thenear-field accumulations of energy.

Non-limiting examples of transmitter sensors 114 include, e.g.,infrared, pyroelectric, ultrasonic, laser, optical, Doppler, gyro,accelerometer, microwave, millimeter, RF standing-wave sensors, resonantLC sensors, capacitive sensors, light sensor, and/or inductive sensors.In some embodiments, technologies for the transmitter sensor(s) 114include binary sensors that acquire stereoscopic sensor data, such asthe location of a human or other sensitive object.

In some embodiments, the memory 106 of the transmitter pad 100 storesone or more programs (e.g., sets of instructions) and/or datastructures, collectively referred to herein as “modules.” In someembodiments, the memory 106, or the non-transitory computer readablestorage medium of memory 106 stores the following modules 107 (e.g.,programs and/or data structures), or a subset or superset thereof:

-   -   information received from the receiver 120 (e.g., generated by a        sensor of the receiver 120 and then transmitted to the        transmitter pad 100);    -   information received from transmitter sensor(s) 114;    -   RF power transmission signals generation module for generating        and transmitting (e.g., in conjunction with unit cell antenna(s)        110) RF power transmission signals (e.g., RF power transmission        signals 422, FIG. 4C);    -   a characteristic selection module for selecting waveform        characteristics of the RF power transmission signals; and/or    -   a beacon transmitting module that transmits (or receives) a        communication signal for detecting a receiver 120 (e.g., within        a near-field transmission range of the transmitter pad 100).

The above-identified modules (e.g., data structures and/or programsincluding sets of instructions) need not be implemented as separatesoftware programs, procedures, or modules, and thus various subsets ofthese modules may be combined or otherwise re-arranged in variousembodiments. In some embodiments, the memory 106 stores a subset of themodules identified above. Furthermore, the memory 106 may storeadditional modules not described above. In some embodiments, the modulesstored in memory 106, or a non-transitory computer readable storagemedium of the memory 106, provide instructions for implementingrespective operations in the methods described below. In someembodiments, some or all of these modules may be implemented withspecialized hardware circuits that subsume part or all of the modulefunctionality. One or more of the above-identified elements may beexecuted by one or more of processor(s) 104. In some embodiments, one ormore of the modules described with regard to memory 106 is implementedon the memory 104 of a server (not shown) that is communicativelycoupled to the transmitter pad 100 and/or by a memory of the electronicdevice and/or the receiver 120. In addition, the memory 106 may storeother information such as certain thresholds and criteria, as well asidentifiers of certain receivers.

Turning to FIG. 1B, a simplified top view of the transmitter pad 100 isillustrated. FIG. 1B shows a wireless power receiver 120 (also referredto as a receiver 120, e.g., a receiver that is internally or externallycoupled to an electronic device) that is placed on top of thetransmitter pad 100 and then receives energy from near-filedaccumulations of energy formed by the unit cell antennas 110. In someembodiments, the receiver 120 includes one or more antennas forreceiving energy from the near-field accumulations of energy formed bythe transmitter pad 100 and a communications component for receivingcommunications (or sending communications) sent by the transmitter pad100. The communications component of the receiver 120 may also includehardware capable of data communications using the variety of wirelessprotocols listed above with reference to the communication component(s)112.

The receiver 120 converts energy from received signals (also referred toherein as RF power transmission signals, or simply, RF signals, powerwaves, or power transmission signals) into electrical energy to powerand/or charge an electronic device coupled to the receiver 120. Forexample, the receiver 120 uses a power converter to convert capturedenergy from power waves to alternating current (AC) electricity ordirect current (DC) electricity usable to power and/or charge anelectronic device. Non-limiting examples of power converter includerectifiers, rectifying circuits, voltage conditioners, among suitablecircuitry and devices.

In some embodiments, the receiver 120 is a standalone device that isdetachably coupled to one or more electronic devices (e.g., electronicdevice 210, FIG. 2). For example, electronic device has processor(s) forcontrolling one or more functions of electronic device and the receiver120 has processor(s) for controlling one or more functions of receiver.In some embodiments, the receiver 120 is a component of the electronicdevice. For example, one or more processor(s) of the electronic devicecontrol functions of the electronic device and the receiver 120. Inaddition, in some embodiments, the receiver 120 includes processor(s)which communicate with processor(s) of the electronic device.

In some embodiments, the receiver 120 receives one or more power wavesdirectly from the transmitter pad 100. In some embodiments, the receiver120 harvests power waves from one or more accumulations of energy (e.g.,accumulation of energy 412, FIG. 4B) created by one or more power wavestransmitted by the transmitter pad 100. As will be discussed in greaterdetail below, the one or more power waves cause accumulations of energyto form at “cutouts” (e.g., cutouts 404-A and 404-B, FIG. 4A) defined ina respective unit cell 110 (e.g., unit cell 400, FIG. 4A). In someembodiments, the transmitter pad 100 is a near-field transmitter thattransmits the one or more power waves within a near-field distance ofits charging surface.

In some embodiments, after energy is harvested from the accumulations ofenergy (as discussed in greater detail below), circuitry (e.g.,integrated circuits, amplifiers, rectifiers, and/or voltage conditioner)of the receiver 120 converts the energy to usable power (i.e.,electricity), which powers the electronic device associated with thereceiver 120 (and/or the usable power is stored in a battery ofelectronic device). In some embodiments, a rectifying circuit of thereceiver 120 converts the electrical energy from AC to DC for use by theelectronic device. In some embodiments, a voltage conditioning circuitincreases or decreases the voltage of the electrical energy as requiredby the electronic device, and may produce a constant voltage forproviding electricity in a form required by the electronic device.

In some embodiments, the receiver 120 harvests energy from near-fieldaccumulations of electromagnetic energy formed by multiple unit cellantennas 110 of the transmitter pad 100. In some embodiments, aplurality of electronic devices may be positioned on a surface of thetransmitter pad 100, each having at least one respective receiver 120that is used to receive power waves from the transmitter pad 100. Insome embodiments, the transmitter pad 100 adjusts one or morecharacteristics (e.g., waveform characteristics, such as phase, gain,amplitude, frequency, etc.) of the power waves to controllably form theone or more accumulations of energy. As described in more detail belowin reference to FIGS. 4A-4C, the transmitter pad 100 may adjust sets ofcharacteristics for transmitting the power waves to account fordifferent receivers and electronic devices housing the receivers (e.g.,distance between the receiver 120 (which may be embedded at differentpositions in different types of electronic devices) and the transmitterpad 100 may vary from one receiver to the next).

In some embodiments, circuits (not shown) of the transmitter pad 100,such as a controller circuit and/or waveform generator, may at leastpartially control the behavior of the unit cell antennas 110. Forexample, based on the information received from the receiver by way of acommunication signal (or data gathered by transmitter sensor(s) 114), acontroller circuit may determine a set of one or more waveformcharacteristics (e.g., amplitude, frequency, direction, phase, amongother characteristics) used for transmitting the power waves that wouldeffectively provide power to the receiver 120. The controller circuitmay also identify one or more unit cell antennas 110 that would beeffective in transmitting the power waves (e.g., receiver 120 may bepositioned between two unit cells, and in such a case, two unit cellantennas may be activated).

As will be discussed in more detail, dimensions (e.g., width, depth, andlength) of “cutouts” in a respective unit cell antenna are selected toreduce far-field gain of the power waves that are used to form thenear-field accumulations of energy on a respective surface of arespective unit cell antenna. For example, the dimensions are selectedso that when a current flows along a respective cutout, a near-fieldelectromagnetic field is generated, and far-field electromagnetic fieldsgenerated by adjacent unit cell antennas cancel, thereby ensuring thatonly near-field accumulations of energy remain, thereby minimizing oreliminating far-field gain.

As also shown in FIG. 1B, the transmitter pad includes a plurality ofunit cell antennas (e.g., unit cell 110-A, . . . unit cell 110-N). Aunit cell antenna is also interchangeably referred to herein as a unitcell, near-field antenna, NF antenna, or non-inductive resonant NFantenna. In some embodiments, the unit cell antennas 110 cover all or aportion of a surface area of the transmitter pad 100. The plurality ofunit cell antennas 110 may contact a top surface (i.e., a chargingsurface) of the transmitter pad 100 (e.g., the unit cells 100 and othercomponents 102 of the transmitter pad 100 may be encapsulated within aplastic or other type of covering).

FIG. 2 is an oblique view of a transmitter pad 200, in accordance withsome embodiments. In some embodiments, the transmitter pad 200 is thetransmitter pad 100 FIG. 1. The transmitter pad 200 includes a housing202 that defines an internal cavity. The internal cavity houses, at aminimum, a plurality of unit cells 110. Moreover, the housing 202 mayalso house other components 102 of transmitter pad 100 (FIG. 1A). Insome embodiments, the housing 202 may be formed using a unibodyconfiguration in which some or all of the housing 202 is machined ormolded as a single structure or may be formed using multiple structures(e.g., an internal frame structure, one or more structures that formexterior housing surfaces, etc.). The housing 202 may be formed of metal(e.g., steel, aluminum, brass, copper, etc.), other suitable materials,or a combination of any two or more of these materials. In someembodiments, at least two portions (e.g., a sidewall and a surface) ofthe housing 202 are made from different materials having differentelectromagnetic properties (e.g., permeability and permittivity). Insome embodiments, the housing 202 is made entirely of a material thatobstructs electromagnetic radiation (e.g., copper, steel, aluminum,etc.).

The transmitter pad 200 includes a conductive layer or plate 204. Insome embodiments, the conductive plate 204 is part of the housing 202(e.g., part of the housing's unibody configuration). In someembodiments, the housing 202 and the conductive plate 204 are separatecomponents of the transmitter pad 200. In these embodiments, the housing202 includes an opening at one end of the housing 202 and the conductiveplate 204 closes the opening. In some embodiments, the conductive plate204 and the housing 202 are made from the same material(s) (e.g., a sametype of metal, such as copper, nickel, etc.). In some embodiments, theconductive plate 204 and the housing 202 are made from at least onedifferent material.

In some embodiments, the transmitter pad 200 also includes a ground orgrounding plate (e.g., grounding plate 308, FIG. 3A). As shown in FIG.3A, an insulator (e.g., a dielectric material) may separate theconductive plate 204 from the grounding plate 308.

In some embodiments, the conductive plate 204 includes a plurality ofdistinct wireless charging regions that are each associated with atleast one unit cell (dotted boxes 206-A and 206-B define respectivewireless charging regions). A wireless charging region is an area of theconductive plate 204 where wireless charging of receiver 212 (e.g.,receiver 120, FIG. 1B) is facilitated due to formation (by respectiveunit cells 110) of near-field accumulations of electromagnetic energywithin one or more of the wireless charging regions. In someembodiments, the plurality of unit cells cover substantially all of asurface area (e.g., 80% or more) of the conductive plate 204. In thisway, a user may wirelessly charge his or her device at various positionson the conductive plate 204. In other words, the user need only placehis or her device including a receiver on the transmitter pad andcharging will occur without needing to be concerned about the exactlocation or orientation of the device.

Each unit cell 206 includes one or more cutouts 208-A and 208-B (e.g.,channels/slots extending through the conductive layer or plate 204) thatfacilitate formation of the near-field accumulations of electromagneticenergy within each of the wireless charging regions. For example, whenRF power transmission signals 422 (FIG. 4C) are transmitted by a feedbeneath wireless charging region 206-A, at least some of the RF signalsreach the conductive plate 204 and excite a current flow 209 around anedge/perimeter of the conductive plate 204 that is along each of thecutouts 208-A, 208-B associated with the unit cell antenna of thewireless charging region 206-A. Based on dimensions of the cutouts 208,arrangement of the cutouts 208, and a direction of the current flow 209at each particular segment of the cutouts 208 (e.g., the current 209 atsegment 214 of the cutout 208-A is flowing in a first direction, asindicated by arrows, and the current 209 at segment 216 of the cutout208-A is flowing in a second direction that is opposite to the firstdirection), the accumulations of energy radiate away from the cutouts208 (e.g., an electromagnetic field radiates away from segment 214 andanother electromagnetic field radiates away from segment 216). Theseaccumulations of energy formed by the RF signals exciting the conductiveplate 204 are also referred to herein as “hot zones” or simply “zones.”As noted above, the receiver may harvest energy from these accumulationsof energy to deliver power or charge to an electronic device coupled tothe receiver.

In some embodiments, each cutout includes a set of dimensions (e.g., awidth, a depth (e.g., thickness of the conductive plate 204), and alength). Characteristics of the accumulations of energy (e.g., height,width, degree of concentration, near-field gain, far-field gain, etc.)formed at the one or more cutouts depend, at least in part, on the setof dimensions of the one or more cutouts. In some instances, the set ofdimensions of a cutout (and in turn, a respective segment of the cutout)are carefully selected based on the requirements of the application sothat characteristics of the accumulations of energy facilitate propercharging of the receiver 212, e.g., a width of the cutout 208-A isselected so that electromagnetic fields radiating from segments 214 and216 of the cutout 208-A at least partially cancel each other out (e.g.,in the far-field region), thereby minimizing far-field gain, while stillcreating accumulations of energy that extend far enough above the outersurface of the conductive plate 204 to deliver power to receivers thatare embedded within electronic devices (and, since they are embedded,the accumulations need to travel above the surface of the conductiveplate 204 to reach these embedded receivers.

In some embodiments, the one or more cutouts in a respective wirelesscharging region all have a same shape. For example, a unit cell withinwireless charging region 206-A includes the first cutout 208-A and thesecond cutout 208-B. As shown, a shape of the first cutout 208-A mirrorsa shape of the second cutout 208-B. Furthermore, in some embodiments,the first cutout 208-A and the second cutouts 208-B are arranged in aninterleaved or interposed fashion (i.e., mated). In doing so,accumulations of energy formed at the first and second cutouts 208-A,208-B cover a threshold amount of surface area associated with thewireless charging area 206-A (e.g., at least 80% of a surface area ofthe conductive plate 204 that is associated with wireless chargingregion 206-A, or some greater (or lesser) amount). Additionally, due tothe interleaved or interposed arrangement of the first and secondcutouts 208, far-field components of electromagnetic fields radiatingfrom respective segments of the first cutout 208-A at least partiallycancel far-field components electromagnetic fields radiating fromrespective segment of the second cutout 208-B (e.g., segments that areadjacent to one another). As such, far-field gain is further reduced.

In some embodiments, adjacent unit cells on the conductive plate 204 arerotated relative to one another. For example, a first unit cell withinwireless charging region 206-A is rotated relative to a second unit cellwithin wireless charging region 206-B, which is adjacent to the firstunit cell. The first unit cell and the second unit cell include cutoutsarranged in the same interleaved or interposed fashion. However, thecutouts in the first unit cell are arranged along a first axis (e.g., avertical axis) and the cutouts in the second unit cell are arrangedalong a second axis (e.g., a horizontal axis), the second axis beingperpendicular to the first axis. Due to the rotated arrangement of theunit cells, some parts of electromagnetic fields radiating from thesecond cutout 208-B at least partially cancel some parts ofelectromagnetic fields radiating from cutout 209 of a unit cellassociated with wireless charging region 206-B. As such, far-field gainis further reduced.

An electronic device 210 is disposed on the outer surface of theconductive plate 204 and is positioned over an additional unit cell (notpictured in FIG. 2). The receiver 212 (e.g., receiver 120, FIG. 1B)embedded in the electronic device 210 is also positioned over thisadditional unit cell. As such, the transmitter pad 200 (e.g.,transmitter pad 100, FIGS. 1A-1B), after detecting the receiver 212, mayinitiate wireless charging of the receiver 212. In some embodiments, thetransmitter pad 200 detects the receiver by receiving (or exchanging) acommunication signal from the receiver 212. Alternatively or inaddition, in some embodiments, the transmitter pad 200 detects thepresence of the receiver via one or more transmitter sensors 114 (FIG.1A). For example, a light sensor of the transmitter pad 200 may detect achange in light inside the internal cavity of the housing 202 when theelectronic device is positioned over one of the cutouts in theconductive plate 204. In another example, an infrared sensor of thetransmitter pad 200 may detect a change in temperature at the conductiveplate 204 when the electronic device is positioned over one of thecutouts in the conductive plate 204. Other types of sensors and sensordata may be used to detect the receiver 212.

It should be understood that although the cutouts 208 are shown with aparticular shape (e.g., a U or horseshoe shape), the cutouts may haveother suitable shapes (e.g., different unit cell antennas within onetransmitter pad could have different shapes). In addition, a size of theelectronic device 210 and the receiver 212 relative to a size of theunit cells 206 shown in FIG. 2 is merely illustrative (e.g., the unitcells may be smaller (or larger) relative to a size on the electronicdevice 210 and the receiver 212).

In some embodiments, a respective unit cell may have dimensions ofapproximately 35 mm by 35 mm. Thus, a transmitter pad that includes a 2by 2 arrangement of unit cells may have dimensions of approximately 70mm by 70 mm. In other embodiments, the transmitter pad may include a 3by 3 arrangement of unit cells, and the transmitter pad may thereforehave dimensions of approximately 105 mm by 105 mm. These are merelyexamples, and other dimensions (for both transmitter pads and individualunit cells) and arrangements of unit cells are also possible.

FIGS. 3A-3D show cross-sectional views of the transmitter pad 200 (takenalong the line A-A′ of FIG. 2), in accordance with some embodiments.Cross-sectional hashing has been removed from antennas 306 and feedelements 307 for clarity.

As shown in FIG. 3A, the conductive plate 204 includes a plurality ofcutouts (e.g., cutout 302-A) extending through the conductive plate 204(e.g., extending from an outer surface of the conductive plate 204through to an inner surface of the conductive plate 204). The conductiveplate 204, and in turn the plurality of cutouts, have a thickness of T1.

The transmitter pad 200 also includes an insulator 304, which isresponsible, at least in part, for projecting the accumulations ofenergy at different distances above the conductor plate 204. Theinsulator 304 separates respective feeding elements 307-A and 307-B froman inner surface of the conductive plate 204. In addition, the insulator304 is sandwiched between the conductive plate 204 and the groundingplate 308. The insulator 304 has a thickness of T2. In some embodiments,the thickness (T1) of the conductive plate 204 is greater than thethickness (T2) of the insulator 304, or vice versa. In some embodiments,the thickness (T1) of the conductive plate 204 is the same as thethickness (T2) of the insulator 304. In some embodiments, the thickness(T2) of the insulator 304 is selected based, at least in part, on theoperating frequency. For example, the thickness (T2) of the insulator304 may range from 0.03λ to 0.5λ of the operating frequency. As notedabove, the transmitter pad 200 can transmit the plurality of RF powertransmission signals at frequencies ranging from 400 MHz (λ=0.75 meters)to 60 GHz (λ=0.005 meters), depending on the application. Accordingly,when operating at a frequency of 400 MHz, the thickness (T2) of theinsulator 304 can range from approximately 0.0225 meters (i.e., 22.5 mm)to approximately 0.375 meters (i.e., 375 mm) and when operating at afrequency of 60 GHz, the thickness (T2) of the insulator 304 can rangefrom approximately 0.00015 meters (i.e., 0.15 mm) to approximately0.0025 meters (i.e., 2.5 mm). One skilled in the art will appreciatethat the thickness (T2) of the insulator 304 can vary from applicationto application and the examples provided above are simply used toprovide context. Therefore, in some embodiments, the thickness (T2) ofthe insulator 304 can range from approximately 0.15 mm to approximately375 mm.

The thickness (T2) of the insulator 304 may modify one or morecharacteristics of the accumulations of energy (e.g., height, width,degree of concentration, near-field gain, far-field gain, resonancefrequency, etc.) radiating from the conductive plate 204. For example,when the insulator has a first thickness (T2′), the accumulations ofenergy may extend above the outer surface of the conductive plate 204 toa first height and when the insulator has a second thickness (T2″), theaccumulations of energy may extend above the outer surface of theconductive plate 204 to a second height, the second height beingdifferent from the first height. Accordingly, the thickness (T2) of theinsulator 304 may influence an overall efficiency of the electromagneticfields radiating from the conductive plate 204.

In some embodiments or circumstances, the thickness of the conductiveplate 204 may also be selected to influence formation of theaccumulations (e.g., the thickness, T1, of the conductive plate 204 isselected to help influence (i) cancellation of parts of electromagneticfields in the far-field region and (ii) accumulations of energy extendfar enough in the near-field region above an outer surface of theconductive plate 204 to deliver power to the receiver 212).

In some embodiments, the insulator 304 is air. Alternatively, in someembodiments, the insulator 304 is a dielectric material (e.g., apolymer, a fiber reinforced polymer, glass, etc.) disposed inside theinternal cavity of the housing 202. As mentioned above, the thickness(T2) of the insulator 304 can influence one or more characteristics ofthe accumulations of energy. In addition, using a first type ofinsulator over a second type of insulator may also influence one or morecharacteristics of the accumulations of energy. In some embodiments, theinsulator 304 supports the conductive plate 204 (e.g., the conductivelayer is formed on the insulating layer and the cutouts are etched fromthe conductive layer and through to the insulator).

The transmitter pad 200 includes a first unit cell 305-A and a secondunit cell 305-B (separated by dashed line). The first unit cell 305-Aincludes a first feed element 307-A and the second unit cell 305-Bincludes a second feed element 307-B. The first and second unit cellantennas 305 may be an example of the one or more unit cell antennas 110(FIGS. 1A-1B). As shown, the first and second feed elements 307 areseparated from an inner surface of the conductive plate 204 by adistance (D). In some embodiments, however, the first and secondantennas are separated from the inner surface of the conductive plate204 by different distances. Variations in the distance (D) may modifyone or more characteristics of the accumulations of energy (e.g.,height, width, degree of concentration, near-field gain, control offar-field gain, etc.) radiating from the conductive plate 204. In someembodiments, to ensure proper forming of the accumulations of energy,the distance (D) is less than the thickness (T2) of the insulator 304.Furthermore, in some embodiments, the distance (D) is less than thethickness (T2) of the insulator 304 by a threshold amount. Put anotherway, a ratio between the distance (D) and the thickness (T2) of theinsulator 304 satisfies a predefined range. For example, the predefinedrange may limit the ratio of (D)/(T2) from 0.05λ to 0.8λ, i.e.,0.05λ<(D)/(T2)<0.8λ. As noted above, at least in some embodiments, thethickness (T2) of the insulator 304 can range from approximately 0.15 mmto approximately 375 mm, depending on the operating frequency of thetransmitter pad 200. Accordingly, in those embodiments, the distance (D)can range from approximately 0.0075 mm (e.g., when operating at afrequency of 60 GHz) to approximately 300 mm (when operating at afrequency of 400 MHz), in light of the predefined range limiting theratio of (D)/(T2) from 0.05λ to 0.8λ.

In those embodiments having dielectric materials disposed in theinternal cavity of the housing 202, the first and second feed elements307 may be at least partially encapsulated by the dielectric material.In doing so, the first and second feed elements 307 (and the otherantennas of the transmitter pad 200) are further supported, and as such,the durability of the transmitter pad 200 is increased (e.g., theinsulator better absorbs impact forces, such as when the transmitter pad200 is dropped). Additionally, interference between the first and secondfeed elements 307 (and other feed elements) is substantially reducedwhen the feed elements 307 are at least partially encapsulated by thedielectric material (i.e., the feed elements 307 are electricallyisolated from one another). In light of this arrangement, an overallefficiency of the transmitter pad 200 is increased.

In some embodiments, the transmitter pad 200 includes a metal patchelement 306 for each antenna element. The feed element 307 drives thecorresponding patch element 306. For example, the first patch element306-A is driven by a first feed element 307-A and the second patchelement 306-B is driven by a second feed element 307-B. The feed element307 may be made from any suitable material known by those skilled in theart (e.g., aluminum, copper, etc.).

In some embodiments, the transmitter pad 200 includes a ground orgrounding layer or plate 308. In some embodiments, the grounding plate308 forms a bottom surface of the housing 202 (FIG. 2). Alternatively,in some embodiments, the grounding plate 308 is placed on top of thebottom surface inside the housing 202. The grounding plate 308 may beformed out of the same material as the housing 202 or may be formed outof a different material. In some embodiments, the grounding plate 308includes a hole (e.g., a via) allowing the feed element (e.g., feedelement 307-A) to pass through the grounding plate 308. Alternatively,in some embodiments, the feed element does not pass through thegrounding plate 308 but instead connects to the antenna element fromsome other direction (e.g., the side). In some embodiments, thegrounding plate 308 acts as a reflector such that RF power transmissionsignals cannot pass through the grounding plate 308 and are reflectedback towards respective cutouts of a unit cell instead.

FIG. 3B is a close-up cross-sectional view of the electronic device 210placed on the conductive surface 204. As shown, the electronic device210, and in turn the receiver 212, are positioned over cutout 302-B(e.g., one of the plurality of cutouts in the conductive plate 204).Accordingly, when the first feed 307-A transmits a plurality of RF powertransmission signals towards the inner surface of the conductive plate204, at least some of the RF power transmission signals of the pluralityof RF power transmission signals excite a current to flow around thecutout 302-B and thereby cause accumulations of electromagnetic energyto form above the cutout 302-B within a near-field distance of theconductive plate 204. The receiver 212 may then harvest energy from theaccumulation of energy formed above the cutout 302-B.

The electronic device 210 includes a sidewall 322 and an internal cavity324 housing the receiver 212. As shown, the receiver 212 is not placeddirectly on an outer surface of the conductive plate 204. Instead, thereceiver 212 is separated from the outer surface of the conductive plate204 by a distance “X” (i.e., a thickness of the sidewall 322).Accordingly, the transmitter pad 200 may adjust one or morecharacteristics (e.g., waveform characteristics, such as phase, gain,amplitude, frequency, etc.) of power waves transmitted by feed element307-A to ensure that an accumulation of energy extends above the outersurface of the conductive plate 204 by at least the distance X. In someembodiments, the transmitter pad 200 adjusts one or more characteristicsof the power waves so that the accumulation of energy extends past thedistance X by a predefined amount, thereby ensuring that the receiver212 can harvest energy from the accumulation of energy.

In some embodiments, the transmitter pad 200 adjusts the one or morecharacteristics of the power waves (e.g., RF power transmission signals422, FIG. 4C) after detecting a presence of the receiver 212. Thetransmitter pad 200 may detect a presence of the receiver 212 using theexample techniques described above.

Alternatively or in addition, in some embodiments, the transmitter pad100 adjusts the one or more characteristics of the power waves afterreceiving one or more communication signals from the receiver 212. Forexample, data contained within the one or more communication signals mayindicate that the receiver 212 is separated from the first feed 307-A bya particular distance. The transmitter pad 200 may determine theseparation distance based on signal strength of the one or morecommunication signals, triangulation, and/or response time (e.g.,receiver 212 timestamps a communication signal when sent which is thencompared against a timestamp of the communication signal when it isreceived at the transmitter pad 200). In some embodiments, thetransmitter pad 200 determines the separation distance using two or moreforms of data (e.g., signal strength in combination with a thermalimaging data, or some other combination). Using the separation distance,the transmitter pad 200 may determine a thickness of the sidewall 322 ofthe electronic device 210 (e.g., subtract fixed distance between feed307-A and the outer surface of conductive plate 204 from the separationdistance to obtain distance “X”).

In some embodiments, the transmitter pad 100 adjusts the one or morecharacteristics of the power waves by considering data obtained from thereceiver 212, data obtained by the transmitter sensors, the set ofdimensions of the cutout(s), and an arrangement of the cutouts.

FIG. 3C is another cross-sectional view 330 of the transmitter pad 200(taken along the line A-A′ of FIG. 2), in accordance with someembodiments. The electronic device 210 and the receiver 212 are notshown in FIGS. 3C-3D for ease of illustration and discussion. Inaddition, some other references, which are included in FIG. 3A, are notincluded in FIGS. 3C-3D for clarity.

In those embodiments where the transmitter pad 200 includes housing 202,the housing 202 includes four sidewalls (e.g., sidewalls 332-A, 332-B,and so on), a bottom surface 334, and an opening defined opposite thebottom surface 334. The opening is configured to receive the conductiveplate 204. In other words, the conductive plate 204 is coupled to thefour sidewalls of the housing 202 such that the conductive plate 204closes the opening.

In some embodiments, the bottom surface 334 is the grounding plate 308(FIG. 3A). Alternatively, in some embodiments, the grounding plate 308is disposed on top of the bottom surface 334 of the housing, asdiscussed above. In those embodiments where the bottom surface 334 isthe grounding plate 308, the bottom surface 334 includes one or moreholes (e.g., vias) allowing one or more feeds (e.g., feed element 307-A)to pass through the housing 202.

In some embodiments, an antenna type may dictate a separation distanceof the antenna from an inner surface of the conductive plate 204. Forexample, referring to FIG. 3A, the first and second feeds 307-A, 307-Bare separated from the inner surface of the conductive plate 204 by afirst distance (D). The first and second feed elements 307-A, 307-B mayfeed metal patches 306-A and 306-B, respectively (e.g., the feed andmetal patches form respective antennas of a first type, patch antennas,that excite the one or more cutouts located above). Additionally, thefeed elements 307-A, 307-B may feed various other antenna types (e.g.,monopole, dipole, magnetic loops, multilayer parasitic-fed antennas,etc.). Now referring to FIG. 3C, first and second feed elements 336-A,336-B are separated from the inner surface of the conductive plate 204by a second distance (J), which is less than the first distance (D). Thefirst and feed elements 336-A, 336-B are a second type of antenna (e.g.,a monopole antenna). Accordingly, depending on the circumstances (e.g.,design restrictions such as a height restriction of the transmitter pad200), one type of antenna may be used over another type of antenna.Moreover, at least in some instances, a complimentary relationshipbetween the one or more cutouts and the feed elements 336-A, 336-Bimproves performance of the transmitter pad 200. An example of the“complimentary relationship” includes a cutout defined through theconductor plate 204 paired with a patch (e.g., micro-strip printed typeof feed element) (as shown in FIG. 3A). One other example includes awire conductor on an outer surface of the conductive plate 204 surfacepaired with a slot style feed. It should be noted that the example aboveis merely illustrative and the result may be opposite, depending on thecircumstances.

FIG. 3D is another cross-sectional view 340 of the transmitter pad 200(taken along the line A-A′ of FIG. 2), in accordance with someembodiments. As shown, the transmitter pad 200 may include one or moreadditional layers disposed on top of the conductive plate 204. In someembodiments, a first additional layer 342 is a dielectric material(e.g., a plastic layer, a glass layer, etc.) that separates theelectronic device 212 from the outer surface of the conductive plate204. Because the first additional layer 342 is a dielectric layer, itdoes not alter an accumulation of energy formed at a respective cutout.However, the transmitter pad 200 has to compensate for a thickness ofthe first additional layer 342 because a separation distance (i.e.,distance “X,” FIG. 3B) between the receiver 212 and the antenna isincreased when the first additional layer 342 is included. In someembodiments, the first additional layer 342 acts as a “lens,” meaning itincreases a degree of concentration (e.g., focuses) of the accumulationsof energy formed near the cutouts. Accordingly, the first additionallayer 342 may improve isolation at specific locations relative to thecenter of the unit cell (e.g., reduce radiation to neighboring unitcells). In addition, the first additional layer 342 uniformlydistributes energy across the outer surface of the conductive plate 204.As a result, gaps (i.e., “cold zones”) between adjacent accumulations ofenergy may be minimized, or even eliminated.

In addition, in some embodiments, the transmitter pad 200 includes asecond additional layer 344 disposed on top of the first additionallayer 342. The second additional layer 344 may be a conductive materialsuch as aluminum or copper. In some embodiments, the second additionallayer 344 is another conductive plate, similar to the conductive plate204. Alternatively, in some embodiments, the second additional layer 344is deposited (e.g., printed, painted, etc.) onto the first additionallayer 344. Again, the transmitter pad 200 has to compensate for athickness of the second additional layer 344 because a separationdistance (i.e., distance “X,” FIG. 3B) between the receiver 212 and theantenna is increased when the second additional layer 344 is included.

In some embodiments, the second additional layer 344 alters formation ofone or more accumulations of energy formed at a respective cutout. Forexample, the second additional layer 344 may increase a concentrationand/or may adjust a position of the accumulation of energy formed at therespective cutout (i.e., may offset a position). In another example, thesecond additional layer 344 can be used to merge one or more portions ofa first accumulation of energy with one or more portions from a second(and perhaps a third) accumulation of energy (i.e., uniformly distributeenergy across the outer surface of the conductive plate 204). In thisway, gaps (i.e., “cold zones”) between adjacent accumulations of energymay be minimized, or even eliminated. In some instances, the secondadditional layer 344 further improves the benefits discussed above withregards to the first additional layer 344.

FIGS. 4A-4C show a unit cell and accumulations of energy that form atrespective cutouts of the unit cell, in accordance with someembodiments. FIG. 4A is a top view of a unit cell 400 (e.g., unit cell110-A, FIG. 1). The unit cell 400 includes a conductive plate 402 (e.g.,conductive plate 204, FIG. 2) having first and second cutouts 404 (e.g.,channels, slots, etc.) defined through the conductive plate 402. Inaddition, the unit cell 400 includes a feed element 406 (e.g., feed307-A, FIG. 3A) located beneath the conductive plate 402 (e.g., locatedin an internal cavity defined by housing 202, FIG. 2). Although the feedelement 406 is shown to be centered in the unit cell 400, in someembodiments, the feed element 406 is not centered (or may be centeredabout a first axis but not centered about a second axis). Placing thefeed element 406 at different positions can influence a distribution ofthe accumulations of energy (e.g., a first position may create a moreuniform distribution and a second position may create a more focuseddistribution).

As shown, each of the first and second cutouts 404 includes a pluralityof portions 408 (also referred to herein as cutout portions). Portionsof a respective cutout may be arranged in numerous ways. For example,the first cutout 404-A includes a first portion 408-A that isperpendicular (e.g., orthogonal) to a second portion 408-B, and a thirdportion 408-C that is also perpendicular to the second portion 408-B.The second cutout 404-B includes similar portions (not labeled). Inanother example, the first portion 408-A may be perpendicular to thesecond portion 408-B, and the third portion 408-C may also beperpendicular to the second portion 408-B, but may extend downwards(instead of upwards as shown in FIG. 4A). These arrangements are merelyillustrative, and other arrangements are possible.

In some embodiments, a shape of the first cutout 404-A mirrors a shapeof the second cutout 404-B (e.g., a horseshoe shape). In addition, thefirst cutout 404-A interleaves or interposes with the second cutout404-B. This arrangement minimizes gaps between the first and secondcutouts (e.g., minimized gaps between respective portions of the firstand second cutouts 404), which results in gaps between adjacentaccumulations of energy also being minimized. In addition, thecomplimentary natural of the cutouts 404 (e.g., the interlockingarrangement) also (i) minimizes far-field gain of the unit cell 400 and(ii) reduces interference with other devices positioned on other unitcells. For example, far-field electromagnetic fields from a respectiveportion of the cutout 404-A is at least partially cancelled out (asdiscussed above with reference to FIG. 2) by far-field electromagneticfields from portions that are adjacent to the respective cutout. Inaddition, due to the interlocking arrangement of the first and secondcutouts 404, far-field gain of electromagnetic radiation is furtherminimized between each of the cutouts.

In some embodiments, each of the first and second cutouts 404 has atotal length that is at least as large as a wavelength of a respectiveRF power transmission signal transmitted by the transmitter pad (e.g.,transmitted by antenna element 406). As such, at least in someembodiments, a length of each portion of the cutouts 404 is less thanthe wavelength of the respective RF power transmission signaltransmitted by the transmitter pad. For example, the second cutout 404-Aincludes first, second, and third portions 408-A, 408-B, and 408-C,respectively, that each have a length of “X,” which is less than thewavelength. However, when the three lengths of “X” are combined fromeach of the three portions, the total length of the cutout 404-A is atleast as large as the wavelength. In some embodiments, the length of “X”is half (or approximately half) the wavelength of the respective RFpower transmission signal transmitted by the transmitter (e.g., V2). Insome embodiments, the length of “X” is some other percentage of thewavelength.

FIG. 4B is a top view 410 of the unit cell 400 showing accumulations ofenergy formed upon transmission of a plurality of RF power transmissionsignals by the feed element 406, in accordance with some embodiments. Asshown, multiple accumulations of energy (e.g., accumulation of energy412) form along a length of each cutout. The number of accumulationscorresponds to the number of portions in a respective cutout. Forexample, the first and second cutouts 404 each include three portions(e.g., first portion 408-A, second portion 408-B, and third portion408-C). As such, the first and second cutouts 404 each include threeaccumulations of energy. In light of this, any number of accumulationsof energy may be created depending on a design of a respective cutout(e.g., a cutout having say, 10 perpendicular portions, facilitatescreation of 10 accumulations of energy). A length of a respectiveportion dictates whether an accumulation of energy forms at therespective portion, and also dictates characteristics of theelectromagnetic field radiating from the respective portion (e.g., anamount of energy present in the accumulation of energy).

FIG. 4C is a cross-sectional view 420 (taken along line C-C′ of FIG. 4B)of the unit cell 400 during transmission of the plurality of RF powertransmission signals 422 by the feed element 406, in accordance withsome embodiments. As shown, transmission of the plurality of RF powertransmission signals 422 by the feed element 406 causes conduction of acurrent along a perimeter of the cutouts 404 located above, therebycausing a plurality of NF accumulations of energy 412-A-412-D to form atthe first and second cutouts 404. The plurality of accumulations ofenergy 412-A-412-D extends above the conductive plate 402 by a distance“Y.” The distance “Y” is greater than the separation distance “X”discussed above with reference to FIG. 3B (e.g., the distance “X”concerns a distance between the receiver 212 and the outer surface ofthe conductive 204). Because of this, each of the plurality ofaccumulations of energy 412-A-412-D can reach a receiver placed on topof the conductive plate 402, thereby facilitating wireless charging ofthe receiver.

In some embodiments, the plurality of accumulations of energy412-A-412-D extends approximately 1 to 5 millimeters above the outersurface of the conductive plate 402. For example, if a receiver isseparated from the outer surface of the conductive plate 402 by 2millimeters, then the plurality of accumulations of energy 412-A-412-Dmay extend above the outer surface of the conductive plate 402 by 2.1 to5 millimeters. In some embodiments, a processor 104 of the transmitterpad 100 (FIG. 1A) modifies one or more characteristics of the pluralityof RF power transmission signals 422 to increase (or decrease) thedistance “Y.” In addition, a variety of variables may be manipulated tocause formation of NF accumulations of energy at various distances fromthe conductive plate 402, and these variables include a thickness of theconductive plate 402, a thickness of the insulator 414 (e.g., insulator304, FIG. 3A), a width of the cutout, a length of a portion, and thetype of antenna may also increase (or decrease) the distance “Y,”depending of types of devices that will be charged using a particulartransmitter pad that includes a plurality of unit cells.

FIGS. 5A-5B show a unit cell and accumulations of energy that form at asingle cutout of the unit cell, in accordance with some embodiments.FIG. 5A is a top view of a unit cell 500 (e.g., unit cell 110-A, FIG.1B). The unit cell 500 includes a conductive plate 502 (e.g., conductiveplate 204, FIG. 2) having a cutout 504 (e.g., channel/slot). The unitcell 500 includes a feed element 506 (e.g., feed element 307-A, FIG. 3A)located beneath the conductive plate 502 (e.g., located in an internalcavity defined by housing 202, FIG. 2). Although the feed element 506 isshown to be centered in the unit cell 500, in some embodiments, the feed506 is not centered (or may be centered about a first axis but not asecond axis).

In some embodiments, the cutout 504 has a total length that is at leastas large as a wavelength of a respective RF power transmission signaltransmitted by the transmitter (e.g., transmitted by antenna element506). In addition, the cutout 504 includes a plurality of portions(e.g., each vertical and horizontal section of the cutout 504). In someembodiments, a length for each portion of the cutout 504 is less than awavelength of the respective RF power transmission signal transmitted bythe transmitter pad (e.g., transmitter pad 200, FIG. 2). In someembodiments, a length of each of the plurality of portions is the same(e.g., λ/2). Alternatively, in some embodiments, a first set of portionsof the plurality of portions has a first length and a second set ofportions of the plurality of portions has a second length, the secondlength being greater than the first length. In some embodiments, thefirst length is a length that facilitates creation of accumulations ofenergy (e.g., λ/2) and the second length is a length that does notfacilitate creation of accumulations of energy (e.g., λ).

FIG. 5B is a top view 510 of the unit cell 500 showing accumulations ofenergy formed after transmission of a plurality of RF power transmissionsignals by the antenna element 506, in accordance with some embodiments.Each of the plurality of accumulations of energy (e.g., accumulation ofenergy 508) forms along a portion of the cutout 504. In someembodiments, each respective portion of the cutout 504 has acorresponding accumulation of energy formed at the respective portion.Alternatively, in some embodiments, one or more portions of the cutouts504 lack a corresponding accumulation of energy formed at the respectiveportion (e.g., when a length of the respective portion does notfacilitate creation of an accumulation of energy).

FIG. 6 is a flow diagram showing a method of wireless power transmissionfor forming one or more accumulations of RF energy at a near-fielddistance with minimal far-field gain, in accordance with someembodiments. Operations (e.g., steps) of the method 600 may be performedby a near-field charging pad (e.g., transmitter pad 100, FIGS. 1A-1B;transmitter pad 200, FIG. 2) or by one or more components thereof (e.g.,an RF power transmission signals generation module, a characteristicselection module, and/or a beacon transmitting module). At least some ofthe operations shown in FIG. 6 correspond to instructions stored in acomputer memory or computer-readable storage medium (e.g., memory 106 ofthe transmitter pad 100, FIG. 1A).

The method 600 includes providing (602) a near-field antenna (e.g., unitcell 400, FIG. 4; unit cell 500, FIG. 5) that includes a conductiveplate (e.g., conductive plate 204, FIG. 2) having (i) first and secondopposing planar surfaces (e.g., an inner surface and an outer surface)and (ii) one or more cutouts (e.g., cutouts 404-A and 404-B, FIG. 4;cutout 504, FIG. 5A) extending through the conductive plate from thefirst surface to the second surface. The near-field antenna furtherincludes a feed element (e.g., feed element 307, FIG. 3A) separated fromthe first surface of the conductive plate via an insulator (e.g.,insulator 304, FIG. 3A). In some embodiments, the feed element is atleast a component of a patch antenna, where the insulator is disposedbetween the feed element and the conductive plate. Alternatively, insome embodiments, the feed element is a component of a patch antennathat is at least partially encapsulated within the insulator. In someembodiments, the conductive plate is a plate specific to the unit cell(i.e., a distinct and separate plate). Alternatively, in someembodiments, the conductive plate extends to one or more adjacent unitcells.

In some embodiments, the near-field antenna further includes anotherinsulator that separates the feed element from a grounding plate (e.g.,grounding 308, FIG. 3A). Alternatively, in some embodiments, theinsulator separates the feed element from the grounding plate.

In some embodiments, the conductive plate is a conductive layerdeposited on a surface of the insulator (e.g., the insulator is a rigidpolymer substrate and the conductive layer is deposited thereon).Alternatively, in some embodiments, the insulator is a dielectric layerthat is deposited on the first surface of the conductive plate.

In some embodiments, the insulator is selected from the group consistingof: a polymer, a fiber reinforced polymer, glass, and air. In someembodiments, a thickness of the insulator is greater than a thickness ofthe conductive plate, or vice versa.

In some embodiments, a first cutout of the one or more cutouts forms afirst meandering line pattern and a second cutout of the one or morecutouts forms a second meandering line pattern. In some embodiments, thefirst and second meandering line patterns are the same meandering linepattern (i.e., a shape of the first meandering line pattern mirrors ashape of the second meandering line pattern). For example, referring toFIG. 4A, a first cutout 404-A forms the first meandering line patternand the second cutout 404-B forms the second meandering line pattern.Alternatively, in some embodiments, the first and second meandering linepatterns are different meandering line patterns. In some embodiments, aline pattern is considered a meandering line pattern when the linepattern includes at least one direction change. In some embodiments, theat least one direction change is a perpendicular direction change.Alternatively, in some embodiments, the at least one direction change issome other angular direction change. One skilled in the art willappreciate that the line patterns in FIGS. 4 and 5 are non-limitingexamples, and other meandering line patterns may be implemented.

In some embodiments, the first meandering line pattern is rotated withrespect to the second meandering line pattern (e.g., rotated 180degrees). Put another way, a shape of the first meandering line patternmay be disposed in a first direction and a shape of the secondmeandering line pattern may be disposed in a second direction, which isopposite to the first direction. For example, as shown in FIG. 4A, thefirst cutout 404-A (i.e., the first meandering line pattern) interlockswith the second cutout 404-B (i.e., the second meandering line pattern)because the two cutouts are disposed in opposing directions.

The method 600 further includes causing (604) the feed element to directa plurality of RF power transmission signals (e.g., RF powertransmission signals 422, FIG. 4C) towards the conductive plate (e.g.,towards an inner surface of the conductive plate 204, FIG. 2). In someembodiments, the plurality of RF power transmission signals istransmitted at a frequency selected from the group consisting of: 5.8GHz, 2.4 GHz, and 900 MHz.

In some embodiments, prior to causing the feed element to direct theplurality of RF power transmission signals towards the conductive plate,the transmitter pad 200 detects a receiver on the conductive plate(e.g., a user places an electronic device 210, which houses the receiver212, on an outer surface of the conductive plate 204, thereby puttingthe receiver within a threshold distance of the wireless charging region206-A, FIG. 2). In some embodiments, the feed element receives the oneor more RF power transmission signals from a power amplifier in responseto determining that a receiver is placed within the threshold distanceof the outer surface. In some embodiments, the threshold distance is apredetermined threshold distance (e.g., the predetermined thresholddistance is stored in memory 106 of the transmitter pad 100, FIG. 1A).

In some embodiments, the transmitter pad 200 detects the receiver usingone or more sensors (e.g., transmitter sensors 114, FIG. 1A).Alternatively or in addition, in some embodiments, the transmitter pad200 detects the receiver by receiving (or exchanging) one or morecommunication signals from (or with) the receiver (e.g., receiving theone or more communication signals via the communications component(s)112, FIG. 1A). For example, a signal strength level associated with theone or more communication signals received by a processor 104 (FIG. 1A)connected to the near-field antenna may indicate that the receiver iswithin the threshold distance of the outer surface. Detecting thereceiver is discussed in further detail above with reference to FIGS. 2and 3A-3B.

The method 600 further includes receiving (606), at the conductiveplate, the plurality of RF power transmission signals from the feedelement. In some embodiments, receiving the plurality of RF powertransmission signals from the feed element causes a current to flow(e.g., current flow 209, FIG. 2) along an edge/perimeter of theconductive plate defined by the one or more cutouts.

The method 600 further includes radiating (608), through the one or morecutouts, at least some of the plurality of RF power transmission signalsso that RF energy from the plurality of RF power transmission signalsaccumulates within a near-field distance of the conductive plate tocreate at least two distinct zones of accumulated RF energy (e.g.,accumulations of energy 412-A-412-D, FIG. 4C) at each of the one or morecutouts. The at least two distinct zones of accumulated RF energy ateach of the one or more cutouts are defined based, at least in part, on(i) a set of dimensions defining each of the one or more cutouts and(ii) an arrangement of the one or more cutouts. For example, the set ofdimensions defining each of the one or more cutouts may include: athickness of the conductive plate, a width of the cutout, a shape of thecutout, a length of the cutout, and a number of portions (e.g.,segments) of the cutout. The arrangement of the one or more cutoutsminimizes gaps between adjacent zones of accumulated RF energy. Inaddition, depending on the arrangement, one or more adjacent zones ofaccumulated RF energy may substantially merge, thereby eliminating gapsbetween the zones of accumulated RF energy.

In some embodiments, the at least two distinct zones cover at least 80%of a surface area of the second surface of the conductive plate.Alternatively, in some embodiments, the at least two distinct zonescover at least 90% of the surface area of the second surface of theconductive plate. A degree of coverage of the surface area is based, atleast in part, on (i) the set of dimensions defining each of the one ormore cutouts and (ii) the arrangement of the one or more cutouts (e.g.,arrangement in a given unit cell and also an arrangement of cutoutsbetween adjacent unit cells).

In some embodiments, a respective cutout of the one or more cutouts hasa respective length that is at least as large as a wavelength of arespective RF power transmission signal of the plurality of RF powertransmission signals. Such a configuration promotes formation of the atleast two distinct zones of accumulated RF energy along the length ofthe respective cutout, as discussed above with reference to FIGS. 4 and5.

Furthermore, in some embodiments, the respective cutout includes, atleast, a first portion defined in a first direction (e.g., first portion408-A, FIG. 4A) and a second portion (e.g., second portion 408-B, FIG.4A) defined in a second direction, the second direction being orthogonalto the first direction. Moreover, a first of the at least two distinctzones of accumulated RF energy is created at the first portion and asecond of the at least two distinct zones of accumulated RF energy iscreated at the second portion.

In some embodiments, the respective cutout further includes a thirdportion defined in the first direction (e.g., third portion 408-C, FIG.4A) or some other direction. In some embodiments, the third portionmirrors the first portion, such that the respective cutout forms ahorseshoe shape. Alternatively, in some embodiments, the third portionextends away from the first and second portions, such that therespective cutout forms an “S” shape. In some embodiments, a thirddistinct zone of accumulated RF energy is created at the third portion.The respective cutout may further include additional portions defined invarious directions.

In some embodiments, the at least two distinct zones of accumulated RFenergy extend no more than 5 millimeters above the second surface of theconductive plate (or some greater (or lesser) amount). In this way,far-field gain of the near-field charging pad is controlled andpotential interference with other devices (or other metallic objects)located in proximity to the near-field charging pad is significantlyreduced, and in some circumstances, completely eliminated.

In some embodiments, the near-field antenna is a first near-fieldantenna (e.g., a unit cell associated with wireless charging region206-A, FIG. 2) and is part of a near-field charging pad (e.g.,transmitter pad 200, FIG. 2) that also includes, at least, a secondnear-field antenna (e.g., a unit cell associated with wireless chargingregion 206-B, FIG. 2) that is positioned adjacent to the firstnear-field antenna within the near-field charging pad. In addition,respective cutouts associated with the second near-field antenna arerotated relative to the one or more cutouts associated with the firstnear-field antenna. For example, the second near-field antenna (e.g., aunit cell associated with wireless charging region 206-B, FIG. 2) may berotated (e.g., 90 degrees) relative to the first near-field antenna(e.g., a unit cell associated with wireless charging region 206-A, FIG.2), or vice versa. Rotating adjacent unit cells, and in turn the cutoutsdefined therein, helps to further increase control over far-field gain,and ensure that the far-field gain is substantially reduced for thenear-field charging pad as a whole. In addition, gaps between adjacentaccumulations of energy (e.g., unit cell to unit cell) are alsominimized (e.g., eliminating “cold zones” on the near-field chargingpad).

FIG. 7 is a flow diagram showing a method of fabricating a near-fieldantenna, in accordance with some embodiments. The near-field antenna maybe an example of a single unit cell (e.g., unit cell 110-A, FIG. 1; unitcell 400, FIG. 4; etc.).

The method 700 includes selecting (702) a set of dimensions for one ormore cutouts (e.g., cutouts 404-A and 404-B, FIG. 4A) to be definedthrough a conductive plate (e.g., conductive plate 402, FIG. 4A) of thenear-field antenna, the conductive plate having opposing first (e.g., aninner) and second (e.g., an outer) planar surfaces. Dimensions for theone or more cutouts are discussed in further detail above.

The method 700 further includes forming (704) the one or more cutoutsthrough the first and second surfaces of the conductive plate in apredefined arrangement (e.g., in an interlocking arrangement as shown inFIG. 4A), each of the one or more cutouts having the set of dimensions.In some embodiments, forming the one or more cutouts includes milling(e.g., CNC milling) the one or more cutouts, laser etching the one ormore cutouts, chemically etching the one or more cutouts, or some othermethod known by those skilled in the art. It should be noted that acutout itself may be formed in a “predefined arrangement,” e.g., thecutout 504 is formed in a predefined arrangement (FIG. 5).

The method 700 further includes coupling (706) an insulator (e.g.,insulator 304, FIG. 3A) to the first surface (e.g., the inner surface)of the conductive plate. The insulator may be mechanically and/orchemically (e.g., using an adhesive) fastened to the first surface ofthe conductive plate. In some embodiments, the insulator supports one ormore regions of the conductive plate.

In some embodiments, the insulator is coupled to the first surface(e.g., the inner surface) of the conductive plate prior to forming theone or more cutouts through the conductive plate (or the insulator isdeposited on the first surface of the conductive plate prior to formingthe one or more cutouts). As such, in these embodiments, forming (704)the one or more cutouts through the conductive plate includes, e.g.,milling through the outer surface of the conductive plate to a surfaceof the insulator coupled to the inner surface of the conductive plate.

The method 700 further includes coupling (708) a feed element to theinsulator. In some embodiments, the feed element is mechanically and/orchemically (e.g., using an adhesive) fastened to the insulator.Alternatively or in addition, in some embodiments, the feed element isembedded, at least partially, within the insulator. It should be notedthat step 708 may be skipped in those embodiments where the insulator isair. In these embodiments, the feed element may be coupled to some otherstructure of the near-field antenna (e.g., a portion of the housing 202,FIG. 2).

In some embodiments, the insulator is a first insulator, and the methodfurther includes coupling a second insulator to the feed element. Forexample, the first insulator may be coupled to a top portion of the feedelement and the second insulator may be coupled to a bottom portion ofthe feed element. In this way, a sandwich structure is formed betweenthe first insulator, the feed element, and the second insulator. Thefeed element may be mechanically and/or chemically (e.g., using anadhesive) fastened to the second insulator. Alternatively or inaddition, in some embodiments, the feed element is embedded, at leastpartially, within the second insulator.

As discussed above, the feed element is configured to direct a pluralityof RF power transmission signals towards the conductive plate and atleast some of the RF power transmission signals of the plurality of RFpower transmission signals radiate through the one or more cutouts andaccumulate within a near-field distance of the conductive surface tocreate at least two distinct zones of accumulated RF energy at each ofthe one or more cutouts. The at least two distinct zones of accumulatedRF energy at each of the one or more cutouts are defined based, at leastin part, on (i) a set of dimensions defining each of the one or morecutouts and (ii) an arrangement of the one or more cutouts. Forming theaccumulations of energy is discussed in further detail above withreference to FIGS. 2-5B.

In some embodiments, the steps of the method 700 may be repeated suchthat additional near-field antennas are fabricated. In addition, in someembodiments, the method 700 further includes forming an array ofnear-field antennas (e.g., an array of unit cell antennas 110-A-110-N,as shown in FIG. 1B). Moreover, in some embodiments, the conductiveplate is a continuous plate associated with each near-field antenna inthe array of near-field antennas. Alternatively, in some embodiments,each near-field antenna includes a distinct conductive plate.

The array of near-field antennas may be interconnected via busing (e.g.,communication bus 108, FIG. 1A) and may further be connected to one ormore processors (e.g., processor(s) 104 of transmitter pad 100, FIG.1A).

In some embodiments, the array of near-field antennas is disposed in ahousing (e.g., housing 202, FIG. 2). In this way, leakage of RF powertransmission signals (e.g., via sidewalls) in substantially reduced, andeven eliminated.

FIG. 8 shows various power distributions (e.g., accumulations of energy)formed on a transmitter pad, in accordance with some embodiments. Inparticular, FIG. 8 shows concentrations of accumulations of energy 802on a transmitter pad (e.g., transmitter pad 100, FIGS. 1A-1B) havingfour unit cells (e.g., unit cell 400, FIG. 4A, unit cell 500, FIG. 5A),and each unit cell is being sequentially activated (e.g., activatedmeaning a feed element for a unit cell starts transmitting RF powertransmission signals). As shown, the accumulations of energy 802substantially cover a surface area of the unit cell 801. In addition,the surface area of the unit cell 801 has minimal cold zones 804. Thisresults from, as discussed above, the set of dimensions defining each ofthe one or more cutouts and an arrangement of the one or more cutouts.

Also, the accumulations of energy 802 are substantially limited to thecurrently activated unit cell (i.e., electromagnetic radiation createdat unit cell 801 does not substantially radiate to neighboring unitcells). The results from the controlled far-field gain and from the unitcells being substantially isolated relative to each other beingminimized. Accordingly, objects on neighboring unit cells are notaffected by radiation emitted from the currently activated unit cell801, nor is an accumulation of energy at a particular unit cell impactedby metal objects that may be placed near to the particular unit cell.

FIG. 9 is a graph that shows an example radiation pattern for a unitcell antenna that includes one or more cutouts, as compared to aradiation pattern for an isotropic antenna that radiates uniformly inall directions. In particular, FIG. 9 shows that the radiation patternfor the unit cell antenna extends above a surface of the unit cellantenna in the near-field range (e.g., 1-5 millimeters) and thatfar-field gain is minimized and controlled to avoid any potentialinterference with other electronic devices operating (or other metalobjects positioned) near the transmitter pad 100 (which includes aplurality of the unit cell antennas 110).

The terminology used in the description of the invention herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the invention. As used in the description ofthe invention and the appended claims, the singular forms “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will also be understood that theterm “and/or” as used herein refers to and encompasses any and allpossible combinations of one or more of the associated listed items. Itwill be further understood that the terms “comprises” and/or“comprising,” when used in this specification, specify the presence ofstated features, steps, operations, elements, and/or components, but donot preclude the presence or addition of one or more other features,steps, operations, elements, components, and/or groups thereof.

It will also be understood that, although the terms “first,” “second,”etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another. For example, a first region couldbe termed a second region, and, similarly, a second region could betermed a first region, without changing the meaning of the description,so long as all occurrences of the “first region” are renamedconsistently and all occurrences of the “second region” are renamedconsistently. The first region and the second region are both regions,but they are not the same region.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A method of fabricating a near-field antenna fortransmitting radio frequency (RF) power transmission signals,comprising: selecting a set of dimensions for one or more cutouts to bedefined through a conductive plate of the near-field antenna, theconductive plate having opposing first and second planar surfaces;forming the one or more cutouts through the first and second surfaces ofthe conductive plate in a predefined arrangement, each of the one ormore cutouts having the set of dimensions; coupling an insulator to thefirst surface of the conductive plate; and coupling a feed element tothe insulator.